Two part, heat curable silicone resins have been used in various industrial applications because of their thermal stability, dielectric properties, mechanical properties, chemical resistance and resistance to atmospheric deterioration. In the electronic industry, these resins have been used as encapsulants and potting compounds for electronic devices such as integrated circuit devices and circuit board mounted power supplies. However, it has been found in certain applications, e.g., as a potting compound for circuit board mounted power supplies, bubbles often become entrapped in the silicone during curing and also rise to the surface of the silicone. Such bubbles adversely affect the reliability of the silicone as an encapsulant or potting material and also cause cosmetic defects when the bubbles break through the surface of the cured polymer. I have now discovered a modifier for such silicone resins which substantially eliminates the aforementioned problems and allows for the potting of such things as board-mounted power supplies with a two part, heat curable silicone resin with little or no formation of surface bubbles or entrapped bubbles.